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Prediction of the time course of the sorption of therapeutic drugs and other solutes by polyvinylchloride in static and dynamic pharmaceutical systems


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Prayurnprohm, P 1994 , 'Prediction of the time course of the sorption of therapeutic drugs and other solutes by polyvinylchloride in static and dynamic pharmaceutical systems', PhD thesis, University of Tasmania.

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Polyvinylchloride (PVC) has several uses and one of these is as the
principal constituent of containers used in the storage of pharmaceutical
solutions. It has been shown previously that the use of PVC containers
for some liquid pharmaceutical systems has not been satisfactory in that
the solute may lose potency with time. Similarly, the use of PVC as a
tubing is not always desirable.
In this work, the effect of each of three physicochemical variables, solute
concentration, electrolyte concentration and temperature on the uptake
of a number of model solutes by PVC infusion bags has been
investigated. Additionally, a study on the kinetics of the sorption of the
model solutes by PVC tubing has been carried out and the influence of
factors such as solute concentration, flow rate, tubing diameter and
tubing length on the extent of solute uptake by PVC tubing has also been
It has been shown that the extent of solute uptake by PVC infusion bags
is independent of the inital concentration of the solute and that both
temperature and electrolyte concentration have significant effects on the
extent of solute loss. The Arrhenius equation is used to describe the
temperature effect on solute uptake into PVC bags. The extent of solute
uptake from solution in the presence of electrolytes without large ions is
a function of increasing ionic strength. A prediction model based on the
diffusion model is used to describe the sorption profile of the model
solutes. It is suggested that the sorption number which has been used to predict solute uptake by PVC bags needs to be adjusted by the use of
correction factors for temperature and for vehicle ionic strength.
A well-stirred compartment model and a well-stirred diffusion model
are examined for their ability to describe the uptake of the model solutes
from aqueous solutions infused through PVC tubings. It is shown that a
biexponential model which is a simplified form of both the well-stirredcompartment
model and the well-stirred-diffusion model can be used to
adequately describe the sorption profiles of the model solutes during a
24-hour infusion period. Furthermore, it is found that, at a certain time
after the beginning of an infusion, the first exponential term of the
biexponential model will approach zero and the biexponential formula
will be reduced resulting in the monoexponential form which is a
general form of the equation used to describe the uptake of all solutes
regardless of their affinity for PVC tubings.
The solute uptake by PVC tubings has been found to be independent of
the initial concentration of the infusion solution while it is shown to be
a function of flow rate, tubing diameter, and tubing length. In order to
describe the difference in the extent of sorption between two separate
kinetic runs conducted with differing flow rate, tubing diameter, and/ or
tubing length, a model based on chemical similarity theory was
developed. This allows for an approximation of the rate and extent of
solute uptake in one system from a knowledge of the uptake in a
separate system operating under different conditions. Results reported
previously by other investigators for a number of drugs and those
predicted using the proposed model are presented.
An attempt was made to correlate the extent of sorption of the model
solutes by PVC infusion bags, or by PVC tubing, with selected
physicochemical properties of the solutes such as octanol-water partition
coefficient, dipole moment, intrinsic molecular volume and
solvatochromic parameters.
The plasticizers used in the formulations of PVC bags and tubings being
studied were identified. The infrared spectra and ultraviolet absorption
spectra of the methanolic extracts of the PVC sheets cut from an
unprinted area of PVC bag and tubing reveal that the phthalate-type
plasticizer, DEHP, was used in both formulations. Therefore, the DEHPwater
partition coefficients were determined for the model solutes and
the utility of this value in predicting the uptake of the model solutes by
PVC materials was evaluated. Some attempts to relate chemical
structure and chemical interaction to solute sorption by PVC infusion
bags are described.

Item Type: Thesis - PhD
Authors/Creators:Prayurnprohm, P
Keywords: Drugs, Drugs, Polyvinyl chloride
Copyright Holders: The Author
Copyright Information:

Copyright 1994 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 1994. Includes bibliographical references (p. 258-275)

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